The M14 rifle, formally the US Rifle, Caliber 7.62 mm, was adopted by the U.S. military in 1957. In January 1968, the U.S. Army officially replaced the M14 with the M16 as the “Standard A” rifle. Although officially phased out as the standard issue rifle, variants of the M14 continued to be used by various branches of the U.S. military, especially as a designated marksman rifle and/or a semiautomatic platform sniper rifle, due to its accuracy and effectiveness at long range.
Recently, there has been a need identified for a battle rifle with greater terminal ballistic performance than the 5.56 mm (.223 caliber) round delivered by the M16 and M4 carbine. The AR10's 7.62×51 mm NATO (.308 Win caliber) provides the desired terminal performance, but has been criticized for sharing the same direct impingement gas system of the M16/AR15. The M14 (or semiautomatic M21) delivers the 7.62 mm round with excellent accuracy. However, the common variants of the M14 stock were more suitable for use by a sniper or designated marksman than as a mainstream battle rifle. Its wooden stock and the polymer variants thereof are not suited for accessory rails or adjustable/interchangeable buttstocks or handgrips.
The M14 has been effectively transformed into a battle rifle by use of a replacement chassis stock system such as that described in U.S. Pat. No. 6,839,998, issued Jan. 11, 2005 and assigned to the U.S. Navy. This stock chassis system is manufactured by Sage International of Oscoda, Mich., out of aluminum or an alloy thereof and requires modification of the barreled rifle action by replacement of the operation rod guide with a member that is bolted to the replacement chassis. The adjustable buttstock assembly is unique to the design, limiting its interchangeability with the wide variety of buttstocks available for the M16/AR15 platform.
Troy Industries, Inc. of West Springfield, Mass., has introduced a “modular chassis system” for the M14 which also replaces the standard stock to provide forward accessory rails and which accepts standardized M16/AR15 buttstocks and handgrips. This chassis is also made entirely of aluminum, but adds significant weight to the weapon system.
The substantial mass of metal used in the chassis system described in the U.S. Pat. No. 6,839,998 patent or the Troy “modular chassis system” to support the barreled action acts as a significant heat sink. Heat generated by the firearm or absorbed from solar radiation will be retained and then radiated to the user. Likewise, when used in low ambient temperature conditions, the mass of metal can rapidly bleed body heat from the user. Injection molded polymer rifle stocks, including for the M14, have been made of various fiber-reinforced resins, including carbon fibers or mixtures of glass and carbon fibers. These stocks, however, are solid in form (with the exception of some portion of the buttstock) or (as shown in U.S. Pat. No. 4,934,084) are a shell requiring internal reinforcement with a resin matrix or (as shown in U.S. Pat. No. 5,615,508) are built up over a foam or wood core in order to provide sufficient strength characteristics. Traditional solid core or injection molded synthetic stocks often include a metal (aluminum) bedding block in order to provide a sufficiently stiff foundation against which to bed the action and/or barrel with epoxy or other bedding material.
U.S. Pat. No. 6,839,998 states that “the chassis 22 may be an assembly of two or more components (such as frame and rails embedded in composite materials).” Accordingly, it was unexpected at the time of the present invention that a stock made of a shell of composite material would provide sufficient strength to be self supporting without the inclusion of an embedded frame or structural core.